Process of casting worm-gear wheels



D. FITZPATRICK.

PROCESS OF CASTING WORM GEAR WHEELS. APPLICATION FILED NOV. I, 1917. RENEWED. AUG. 14. I520.

.1,35819Q v PatentedNov. 9,1920.

6 x a a.

UNITED STATES PATENT OFFICE DAVID FITZPATRICK, OF CLEVELAND, OHIO, ASSIGNOR TO THE CLEVELAND WORM AND I GEAR'COMPANY, 0F CLEVELAND, OHIO, A CORPORATION OF OHIO.

PROCESS OF CASTING WORM-GEAR WHEELS.

Specification of Letters Patent.

Patented Nov. 9, 1920.-

Application filed November 1, 1917, Serial No. 199,750. Renewed August 14, 1920. Serial No. 403,512.

' an improvement in the method of constructing worm gears in which a relatively weak metal, such as bronze, is mounted on an iron center.

Heretofore, it has been customary to cast the iron centers with means for interlocking with a weaker metal such as bronze which, in a molten condition, is poured around the periphery of the iron center or core and flows into the recesses which are provided therein. The recesses have been either in 1 the form of grooves or spaces between projecting lugs.

5 the following particular description of one The object of this invention is to make a stronger joint between the two metals composing the wheel and to prevent one metal leaving the other under any circumstances, such as creeping or breaking apart.

Various-other objects and advantages of the invention will be in part obvious from an inspection of the accompanyingdrawings and in part will be more fully-set forth in embodying "my invention that is brokenaway inpart to show more clearly the construction thereof; f 7 Fig. 2 represents a plan view-of the rim of-the worm gear center or core; I

Fig. 3 is a sectional view on the line 33 ofFig. 1;, Fig. 4 is a sectional view on the line 4-4 ofFig.1.' v

The iron center a maybe of cast iron,

malleable iron, steel or a suitable alloy. The

rimor periphery of t e center is provided with stubs 6 extending part way across its face. [Aring ofrelatively weak anti-fr ction material such as bronze or a similar alloy 0 provides the outer portion of the Wheel and has the gear teeth formed therein. The stubs b register with the teeth and are spaced apart to form an annular grooved that is filled with the antifriction material and prevents lateral movement of the ring. The inner ends of the stubs are also undercut as at e to form interlocks with the bronze. Small passages may also be provided inthe rim of the core which become filled with the anti-friction material durin casting and form locking loops f, but sucli locking loops are not essential and may be added as an additional precaution.

The outer ring of bronze or similar antiiriction metal is Welded or brazed onto the iron center or core at the time it is cast so as to form practically a unitary structure, and the process by which this is accomplished is as follows: The rim of the cast iron core is first thoroughly cleansed and it is then washed with a weak solution of muriatic or similar acid. Promptly thereafter the rim is coated with molten tin or a suitable alloy of tin such as tin and lead. This coating may be comparatively thin such for example as would be formed by dipping the rim into a bath of the coating material'iand then allowing it to drain. The coating hardens immediately after being applied to the core.

Thereafter and just before casting, the

core itself s heated to a temperaturethatwill caus the coating to soften Without melting or draining. Preferably the core is vided for this purpose. After the bronze has set, the wheel is taken out and allowed to cool gradually to normalatmospheric Subsequently the teeth are temperature. out in the bronze inthe well known manner. By meansof this process a gear wheel is produced having a bearingface ofa com paratively weak anti-friction material such under the most severe conditions of actual use, the ring cannot creep or Work loose and the joint will be one of the strongest points in the wheel.

While I have shown and described and have pointed out in the annexed claim, certain novel features of my invention, it will be understood that various omissions, substitutions andchanges in the form and details of the device illustrated and in its operation may be made by those skilled in the art Without departing from the spirit of the invention. I

Having thus described my invention, I claim:

The process of forming a gear having a center core of cast iron and a surrounding ring of bronze which consists in coating the core with a substance containing tin, permitting the coating to harden, heating the coated center to a temperature of approximately 300 F. to soften the substance and casing the bronze on said softened substance to braze the parts together.

Signed at Cleveland, in the county of Cuyahoga, and State of Ohio this 18th day of October, 1917.

Davin FITZPATRICK. 

